Year Observations     Objects
1950            2          1 
1951            6          3 
1953            4          2 
1954            2          1 
1955            4          2 
1956            2          1 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978            8          3 
1981            4          2 
1982           12          6 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990           32         14 
1991          471        179 
1992          743        301 
1993         1308        487 
1994         1681        617 
1995         3081       1075 
1996         2980       1053 
1997         1866        644 
1998        21858       9277 
1999        13560       5202 
2000        38674      15988 
2001        39480      15337 
2002        35026      15216 
2003        57819      24058 
2004        46400      17802 
2005        81560      25106 
2006       105233      33772 
2007       192101      59368 
2008       112782      32285 
2009        93523      26355 
2010       133269      36263 
2011       158690      44010 
2012       149924      41539 
2013       222054      63259 
2014       565640     144101 
2015       798554     210110 
2016       659691     171402 
2017       555175     150309 
2018       353012      99172 
2019       866281     211478 
2020       619440     157686 
2021       834477     198183 
2022       622924     178300 
2023       560443     160300 
2024       621478     179031 
2025       206360      58973